Photoconductor squaraine

The semiconductor selenium is an excellent photoconductor however, its photoresponsiveness decreases sharply at wavelengths over 550 nm, which has motivated research on organic photoconductive materials.1550,1551 Many different organic compounds display photoconductive behaviour, such as phthalocyanines (596 M = metal) or squaraines (597) (Figure 6.33) today more than 90% of xerographic photoreceptors are composed of organic photoconductors. 

The number of studies on squaraines has grown significantly in recent years, especially for the development of fluorescent materials, photoelectrochemical batteries, photoelectric conversion elements [78], substrates for photovoltaic cells, photoreceptors, and photoconductors [79]. Squaraine derivatives with well-differentiated behavior can be obtained by tailoring the substituent type. As a result of this tuning, a large variety of compounds has been described in the literature [61, 67, 69a, 71, 79]. In our group, we are interested in squaraines [20, 78, 80] which carry anilines and aliphatic groups as substituents. 

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